Abstract: Circuit for detection of an asymmetry in the magnetization current, generated by a reference alternating voltage, in a magnetic modulator, in particular a magnetic modulator for zero-flux detection. This magnetic modulator comprises two virtually identical, wound magnet cores (T2, T3), each with a primary winding (W1) to be fed with a modulating current (i.sub.1) and a series circuit of an auxiliary winding (W3) and an impedance (Z2, Z3) across which a voltage proportional to the magnetization current arises during operation. The reference alternating voltage (U.sub.m) is fed to the respective series circuits (W3, Z2; W3, Z3) such that no resultant induction current is induced in the modulating current (i.sub.1). The voltages over the impedances (Z2, Z3) form input signals for two peak value detectors (PD1, PD2), the strength of the output signal of which represents the degree of asymmetry of magnetization current.

Abstract: Superconducting rectifier for the conversion of a relatively low current from an alternating current supply source into a relatively high direct current, essentially consisting of a transformer, at least the secondary coil of which is constructed in semiconducting form, and superconducting switches for the passing of the alternating current induced in the secondary transformer coil through a load, in which the superconducting switches means consist of a commutating part and a blocking part which function independently of each other and are connected in series, and in which the increase in resistance (R) which the commutating part produces upon opening the switching means fulfils the condition ##EQU1## being appreciably lower than the increase in resistance which the blocking part produces upon opening the switches means.

Abstract: Current measuring system particularly suitable for use as an earth leakage detection system and functional device equipped with such a system e.g. an earth leakage switch.